body {
  padding: 300px;
}
.cart {
  width: 150px;
  position: relative;
}
.cart:hover > .list {
  display: block;
}
.cart:hover > .btn {
  border-bottom-color: transparent;
}
.cart .btn {
  border: solid 1px #ddd;
  padding: 10px;
  box-sizing: border-box;
  font-size: 14px;
  background: #fff;
  position: relative;
  top: 1px;
  z-index: 1;
}
.cart .list {
  padding: 10px;
  width: 300px;
  border: solid 1px #ddd;
  right: 0;
  position: absolute;
  background-color: #fff;
  display: none;
  margin-top: -1px;
}
